1. Field of the Invention
The present invention relates to a method of probing ion implantation, and more particularly to a method for probing the error of energy and dosage in the high-energy ion implantation.
2. Description of the Prior Art
A conventional method of probing ion implantation is applied via a thermal probe method. The method can easily measure a thermal wave signal value (TW) from the ion-implant induced damage in a semiconductor substrate. A .beta. silicon wafer is used as a test wafer. Afterward, an ion implantation process is performed, and phosphorous impurities or boron impurities are implanted into the test wafer. As the implanted ions move through a crystal lattice, they displace atoms in their path and thus cause a substantial amount of crystal graphic damage. Then thermal waves are introduced in the test wafer by laser beam heating, and the ion-implantant-induced damage will generate a thermal wave signal value (TW). The method can detect the ion implantation state such as the concentration and the depth of implanted ions via the thermal wave signal value (TW). The thermal probe is easily operated and the probing speed is very rapid. The time of thermal probing is in a range of about 5 minutes to 10 minutes. However, the method is limited to detect the depth of ion diffusion via the thermal probe. The thermal probe can not effectively probe the deep ion state introduced in the test wafer. Therefore, while the high-energy ion implantation is performed, the thermal probe can not probe the entire ion state beneath the surface of the substrate. The thermal probe will only detect the shallow ion state from the ion-implant-induced damage via laser beam heating, which will cause a reduction of thermal wave signal value (TW) and an increase of sigma (.delta.). The result generates a poor uniformity of ion concentration distribution.
Additionally, While the thermal probe is applied to detect TW, it is difficult to decide the error source of the ion implantation that is from either energy or dosage. When the thermal probe is performed, the non-normal state about TW may be happened. If the error source is not from the extra condition such as the unsteady state of thermal probe, the mistake of the test wafer, or the mistake of the implanted program, etc., it is really difficult to find the problem source only via TW. However, the structure of ion implanter is very complex. Therefore, it usually spends a lot of time to detect the machine before finding the problem source. Accordingly, the conventional method will influence the uptime of the machine and can not effectively probe the error source that is from either the energy or the dosage non-normal in a high-energy ion implantation.